synapses

• Nueral com

  • Cell body life support
  • Dendrites recieve messages from toher cells
  • Axon passes messages away from cell bod
  • Neural impulse elec sig traveling down the axon
  • Myelin sheath covers axon of neuron
  • Terminal branches of axon form junctions w other cells

  
• Bystander Stress vs. actual stress The mere presence of another animal that had experienced stress
• The Resting MP for a typical neuron is about -70mv
• The Membrane potential the electrical charge across a cell membrane Difference between the electrical potential within and outside the cell
• Depolarization Reduction (towards 0) of the membrane potential of a cell from its normal resting potential
• Hyperpolarization An increase in the membrane potential of a cell relative to the normal resting period
• Action potential Brief electrical impulse that provides the basis of conduction of information
• Threshold of excitation The value of the membrane potential that must be reached to produce an action potential
• Membrane potential

  The electrical charge in the nerves is a result of the balance between two opposing forces

  Diffusion: Movement of molecules from high concentration to regions of low concentration

  Electrostatic pressure: Attractive/Repulsive atomic force
• Resting Potential

  Electrical properties present when neurons are at rest

  Caused by ions within and outside the cell

  (+) charged Na and K ions and (-) charged Cl ions

  Distribution is uneven as the cell membrane allows certain ions to pass in and out through channels
• Action Potential

  Firing of the cell’s message (Nerve Impulse)

  Two types of messages: Excitatory and Inhibitory

  Refractory period: follows generation of action potentials.
• • . Na- channels open and Na- enters the cells
  • K+ channels open, K+ begins to leave cell
  • Na- channels become refractory, no more Na- enters the cell
  • K+ continues to leave cell, causes membrane potential to return to resting level
  • K+ Channels close, Na- Channels reset
  • Extra K+ outside diffuses away
• Neurons communicate by means of the neurotransmitters released by terminal buttons into the synapse.
• Chemicals used to transmit information between cells are:

  • Neurotransmitters
  • Neuromodulators
  • Hormones
  • Cells that contain receptors for hormones are referred to as Target Cells
• Astrocytes

  Monitor and control levels of ions in the extracellular space

  Possess receptors for many neurotransmitters

  Facilitate synaptogenesis
• Schwann cells Axonal regrowth in PNS
• Oligodendrocytes

  Role in major depression
• Mirror Neurons

  Neurons that respond when engaging in a behavior and when observing that behavior
• Epilepsy as synchronized excitability

  • Persist from seconds to minutes.
  • Partial seizures originate in a localized area
  • Generalized seizures originate in distributed area